1. Field of the Invention
This invention relates to a promoter of phytosulfokine precursor derived from rice and a transgenic plant produced by incorporation of the promoter to activate expression of an exogenous structural gene.
2. Description of Related Art
In the field of plant genetic engineering, a promoter is ligated to upstream of an exogenous gene of target, which is a conventional technique for over-expression of the exogenous gene. In many cases, expression of the exogenous gene is not sufficient without existence of such promoter. Various promoters are utilized for this purpose and the method using cauliflower mozaic virus is the most conventional technique in this art. Here, a promoter means a regulatory region existing 5xe2x80x2-upstream of a structural gene. It is known that binding of RNA polymerase to a promoter serves as an initiation signal of transcription.
The method utilizing cauliflower mozaic virus (CAMV) 35S promoter is an excellent method for over-expression of an exogenous gene. However, in some cases, the extent of expression of the exogenous gene is not sufficient, depending on the exogenous gene to be incorporated and the species of the host plant which is the target of gene incorporation. Thus, there have been strong demands on a promoter with higher activity. It is the object of this invention to obtain a novel promoter exhibiting higher potency to activate a structural gene, compared with the conventional CAMV35S promoter.
The inventors noticed phytosulfokine (PSK), which is a peptide growth factor of a plant, and performed investigation on the growth factor. PSK is one of growth factors contained in so-called xe2x80x9cconditioned medium:CMxe2x80x9d, a medium once used for cell culture. It is known that PSK is secreted into extra-cellular medium and functions in the manner like autocrine. At performance of plant cell culture, various known hormones or nutritional elements are added to the culture medium as a conventional technique. However, in some plant species, cell culture is itself difficult or rate of cell proliferation is extremely slow. Moreover, when the density of a plant cell is lower than necessary, proliferation of the plant cell becomes difficult. Even in such cases, PSK is effective to enhance proliferation of a plant cell. It is also known that, the structure of PSK-xcex1 and PSKxcex2 are defined by the following sequences wherein tyrosine residues of the PSKs are sulfated by post-translational modification.
PSK-xcex1: Tyr(SO3H)xe2x80x94Ilexe2x80x94Tyr(SO3H)xe2x80x94Thrxe2x80x94Gln
PSK-xcex2: Tyr(SO3H)xe2x80x94Ilexe2x80x94Tyr(SO3H)xe2x80x94Thr
The PSK-xcex1 and PSK-xcex2 are extra-cellular secreted peptides bio-synthesized in the form of their precursor, sulfated and processed during their transition via trans-Golgi network. The cDNA sequence of Oryza sativa phytosulfokine (OsPSK) have been already determined, using the technique of cDNA cloning. Moreover, the cDNA thus obtained and the polypeptide encoded by the cDNA are described in Japanese Patent Publication No. 11-079612. Incorporation of said gene into a plant would enhance proliferation of a plant.
One aspect of this invention is a promoter consisting of a base sequence of following (a), (b) or (c):
(a) a base sequence represented by base numbers xe2x88x923359 to xe2x88x921 shown in SEQ:ID NO:1 in the sequence list,
(b) a base sequence in which a part of said base sequence (a) is deleted or another base sequence is added to said base sequence (a) or a part of base sequence (a) is substituted with another base sequence, the base sequence (b) exhibiting activity to enhance expression of a structural gene existing downstream of the promoter, or
(c) a base sequence that hybridizes with the base sequence (a) under stringent conditions.
Further aspect of this invention is a promoter consisting of a base sequence of following (d), (e) or (f):
(d) a base sequence represented by base numbers xe2x88x921911 to xe2x88x921 shown in SEQ:ID NO:2 in the sequence list,
(e) a base sequence in which a part of said base sequence (d) is deleted or another base sequence is added to said base sequence (d) or a part of base sequence (d) is substituted with another base sequence, the base sequence (e) exhibiting activity to enhance expression of a structural gene existing downstream of the promoter, or
(f) a base sequence that hybridizes with the base sequence (d) under stringent conditions.
Further aspect of this invention is a promoter consisting of a base sequence of following (g), (h) or (i):
(g) a base sequence represented by base numbers xe2x88x921034 to xe2x88x921 shown in SEQ:ID NO:3 in the sequence list,
(h) a base sequence in which a part of said base sequence (g) is deleted or another base sequence is added to said base sequence (g) or a part of base sequence (g) is substituted with another base sequence, the base sequence (h) exhibiting activity to enhance expression of a structural gene existing downstream of the promoter, or
(i) a base sequence that hybridizes with the base sequence (g) under stringent conditions.
Further aspect of this invention is a promoter consisting of a base sequence of following (j), (k) or (l):
(j) a base sequence represented by base numbers xe2x88x92563 to xe2x88x921 shown in SEQ:ID NO:4 in the sequence list,
(k) a base sequence in which a part of said base sequence (j) is deleted or another base sequence is added to said base sequence (j) or a part of base sequence (j) is substituted with another base sequence, the base sequence (k) exhibiting activity to enhance expression of a structural gene existing downstream of the promoter, or
(l) a base sequence that hybridizes with the base sequence (e) under stringent conditions.
Further aspect of this invention is a gene encoding phytosulfokine precursor consisting of a base sequence represented by base numbers xe2x88x923359 to 2033 shown in SEQ:ID NO:5 in the sequence list.
Further aspect of this invention is a plasmid in which above described promoter was incorporated. Moreover, a transgenic plant cell in which above described promoter was incorporated to activate expression of a structural gene existing downstream of the promoter is also within the range of this invention. Moreover, a transgenic plant body in which above described promoter was incorporated to activate expression of a structural gene existing downstream of the promoter is also within the range of this invention.
Further aspect of this invention is a method to activate expression of an endogenous structural gene or an exogenous structural gene in a plant by incorporation of above described promoter into upstream of the structural gene.